1. Field of the Invention
The present invention relates to metered dose inhalers, and, more particularly, to a pump for a metered dose inhaler which does not require the use of a pressurized container of medicine.
2. Brief Description of Related Art
Metered dose inhalers have been commercially available for use in the treatment of a variety of respiratory ailments, such as asthma. Such metered dose inhalers typically require a pressurized cylinder or canister of medicine to deliver a metered dose of such medicine to a person's respiratory tract. These pressurized cylinders or canisters have employed a halogenated hydrocarbon as a propellant, with the active compound dissolved in the propellant or suspended in the propellant in solid, micronized form.
For example, U.S. Pat. No. 4,955,371 describes a disposable inhalation device wherein an aerosol measured dose canister provides a short spray for releasing a fixed dose of medicine. However, environmental concerns have disfavored the use of halogenated hydrocarbons in aerosol containers. U.S. Pat. No. 4,534,345 describes a dosage inhaler employing a dosing unit for dosing a pharmacologically active compound separate from a pressurized propellant container. The pressurized container contains liquified, pressurized carbon dioxide. In either case, the propellant is delivered into a person's respiratory tract with the medicine dose.
Thus, there is a need for a metered dose inhaler capable of delivering a metered dose of an active compound without the use of a pressurized propellant. Therefore, in order to alleviate these and other problems, an objective of the present invention is to provide a metered dose inhaler pump for pressurizing and delivering a metered dose of an active compound to a person's respiratory tract.